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I set up a CentOS6-XEN4-Server according to these instructions.

Now I want to set up bridges - first manually:

brctl addbr test - but this fails with:

"add Bridge failed: Package not installed"

Googling about that I tried to manually modprobe bridge which triggers an error that is caused-according to dmesg by:

bridge: Unknown symbol ipv6_dev_get_saddr (err 0)

modinfo bridge reveals that the bridge-modules depends on stp,llc and ipv6.

Great. I do not want IPv6, I do not need IPv6 and have blacklisted IPv6.

  1. Is there any way to get brctl running without enabling IPv6?

  2. Why is that depency there at all?

Update 2014-05-14

I found this to be a general CentOS 6/RH 6 problem. It also applies to the bonding module.

The accepted answer describes the root-cause - so this problem will also arise on comparable kernel-versions and is not restricted to CentOS/RedHat/Scentific Linux 6.

share|improve this question
Disabling IPv6 is a serious mistake. You do need it, if not today (or even years ago!) then very soon. – Michael Hampton Jan 14 '14 at 16:28
@MichaelHampton on directly internet connected systems maybe. On intranet, linux-systems - nope. – Nils Jan 14 '14 at 21:56
You need it even more on internal systems! Perhaps you don't yet understand IPv6... – Michael Hampton Jan 14 '14 at 21:58
up vote 1 down vote accepted

it has been discussed on the kernel ML and the conclusion was that users shouldn't disable ipv6 anymore.

quoted from

The workaround for this situation is to not blacklist the ipv6 module, but rather set its disable_ipv6 module option. That way the code gets loaded, but no ipv6 functionality is registered with the kernel so user space can't accesses it.

Update 2014-05-14:

The correct workaround seems to be:

  1. Un-blacklist ipv6 and net-pf-10
  2. create /etc/modprobe.d/ipv6.conf with the following content:

    options ipv6 disable_ipv6=1

share|improve this answer
Excellent reference - although I would not name RH-bugzilla a kernel-ML. Interesting option for the IPv6-module. – Nils Jan 14 '14 at 21:59
i was actually referring to another ML (LKML) where this topic has been discussed as well. – alxgomz Jan 14 '14 at 23:45
BTW: There seems to exist the same problem with the bonding-module. – Nils May 13 '14 at 15:01

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